Such an adjusting drive is disclosed by DE 33 18 935 -C1-. The transmission for coupling the drive unit driven by an electric motor to the steering column tube has a metallic worm gear that engages in globoidal worm gearing on the steering column tube, which is also made of metal, so that the steering column tube can be adjusted in both axial directions relative to the housing by an electric motor which is reversible in direction of rotation. Such a transmission is self-locking and therefore avoids additional locking elements for fastening in the set position. To minimize play in the gearing and transmission, the worm gear is mounted to pivot around a shaft running parallel to the longitudinal axis of the gearing on the steering column tube and is loaded by a spring against the gearing on the steering column tube. Instead of such a spring, a hand-operated eccentric adjusting device can also be used.
Adjusting drives of the usual design require an undesirable increase of weight with the adverse consequences resulting from this, especially in case of a frontal collision of the vehicle.